The first release candidate for Prototype 1.6.0 is now [available for download](http://prototypejs.org/2007/8/15/prototype-1-6-0-release-candidate). This version features a rewrite of the event system, including support for DOM-based custom events and the DOMContentLoaded event, true class inheritance and superclass method references, and improvements to the DOM, Ajax, and function APIs. Please give it a spin in your apps and [let us know](http://dev.rubyonrails.org/) if you run into trouble.